In Saw, Detective David Tapp investigates a series of crime scenes linked to the same murderer. The victims have been placed in to traps that attempt to teach them to appreciate their life, a quality they decidedly lack. The victims who fail these "tests" have a jigsaw piece cut out of their bodies. This has earned the killer the alias The Jigsaw Killer by newspaper writer Oswald Mcgullicuty.[2]Saw II later reveals these missing pieces have been intended to show the missing survival instinct of Jigsaw's victims.[3]

At one of the crime scenes, Tapp and his partner, Steven Sing, discover a penlight with fingerprints on it. Forensics indicate that the fingerprints belong to Doctor Lawrence Gordon, who is coaxed to the police station for questioning. Saw V later revealed that Jigsaw accomplice Mark Hoffman had planted this penlight to arise suspicion on Gordon.[4] While a few victims have already been discovered, one victim named Amanda Young manages to survive her test. Lawrence watches while Tapp interrogates Amanda for her testimony. After hearing her testimony, Tapp gives Lawrence a ride home and becomes more suspicious that Lawrence is Jigsaw.[2]

Tapp recovers and studies the video tape left at Amanda's trap location and deciphers the location of Jigsaw's lair. Tapp and Sing find Jigsaw in his lair, but fail to arrest him due to Jigsaw non-fatally slashing Tapp's neck and Sing falling victim to one of Jigsaw's traps. Following Sing's death, Tapp becomes unstable and begins to obsess over catching Jigsaw, causing him to be discharged from the police force and to be divorced from his wife.[2]

As Jigsaw was able to hide his identity when his lair was raided, Tapp still believes that Lawrence is Jigsaw (ironically, this would foreshadow Lawrence later becoming Jigsaw's accomplice in Saw 3D), and spends much of his time to harass and pester him, unknowing that Lawrence had been abducted and is currently in a trap of his own. This causes him to stake out his home; he uses a video camera to watch it from another apartment. During this, Tapp sees Zep Hindle at the Gordons' house and then hears gunshots coming from the house. Tapp responds and discovers that Alison Gordon and her daughter Diana are being held hostage by Zep. A gunfight ensues, allowing Alison and Diana to escape. Tapp chases Zep to the site of another Jigsaw game, later revealed to be Lawrence's trap. Before discovering the trap site, Zep and Tapp engage in a brief struggle, and Tapp is shot in the chest, leaving him alone to die in a sewer.[2]

The scene where Daniel Rigg is watching Jill Tuck's interrogation at The Metropolitan Police Department features a very brief picture of David Tapp. He is briefly seen as Rigg looks through a folder containing pictures of several police officers he has lost. The picture of Tapp is the same picture that becomes framed and shown at the memorial in the fifth film.

In Saw V, a memorial service is held for the deceased officers from the Jigsaw murders. Tapp's police picture is held next to his partner Steven Sing.[5][6] He appears in a flashback, inquiring Dr. Gordon about the penlight Mark Hoffman planted. Danny Glover was set to make a cameo appearance as David Tapp in Saw V but could not show up due to scheduling issues. The scene was originally for Tapp to attend Seth Baxter's murder scene, but was changed with Hoffman instead.[7]

In the video game Saw, Tapp is healed by Jigsaw after being shot in the chest during the first Saw film. He is brought to the abandoned Whitehurst asylum where he is placed in the "Reverse Bear Trap" Amanda Young was in. He quickly escapes after Jigsaw scolds him for his lack of appreciation for his life and the lives of others.[5][8] Upon escaping, Tapp ventures through the asylum where he faces others during their tests. Some of these tests involve Tapp in numerous ways. Tapp's first major test is to save Amanda Young, the woman he interrogated during Saw, unbeknown to him that she had become Jigsaw's secret apprentice. Upon saving her, she stages her kidnapping by another Jigsaw apprentice called Pighead and Tapp moves to his next test. The second test is for Jennings Foster, a fellow officer of Tapp's who had committed a hit-and-run which he framed an innocent person for. A conflicted Tapp saves Jennings who runs away and blames Tapp for being there.[5]

David Tapp as he appears in Saw: The Video Game. Tapp is shown in the series signature "Reverse Bear Trap".

Tapp's third test is for Melissa Sing, the widow of Tapp's former partner Steven Sing who has since become a neglectful mother to her son. Jigsaw informs her that Tapp had ignored calling for backup or getting a search warrant when searching Jigsaw's lair in the first Saw film, a careless step which was the reason Steven was killed.[9] Believing Tapp could have prevented his partners death, Melissa began to blame him for her misfortunes. Upon Tapp finding and saving her, Melissa leaves Tapp to deal with his other tests.[5]

Tapp proceeds to save Oswald Mcgullicuty, a newspaper writer who coined the alias "Jigsaw", and begins to accuse Tapp of being Jigsaw. After saving Oswald, Tapp rescues Obi Tate, an arsonist who wanted to be tested by Jigsaw. Tapp then proceeds to save his sixth victim, Jeff Ridenhour, who was in the "Drill Trap" when Tapp and Sing had raided Jigsaw's lair during Saw. After he survived his first test, Jeff becomes suicidal after Tapp harasses him to discover Jigsaw's identity. This causes Jeff to be placed in his second trap in which Tapp saves him.[5]

After saving all of the victims in the asylum, Tapp kills Pighead and proceeds to Jigsaw. He labels Tapp as a murderer for killing Pighead and others in Whitehurst. Tapp finds and chases Jigsaw but finds two doors labeled "Truth" and "Freedom".[5] If the player chooses the "Freedom" door, Tapp escapes and is labeled as a hero, but he kills himself due to the stress of not being able to catch Jigsaw. If the player chooses the "Truth" door, Tapp chases Jigsaw and catches him, but he finds that it was Melissa Sing. A tape recorder informs Tapp that Melissa was assigned by Jigsaw to watch over Tapp's test and that her son would be killed if she did not. Melissa then breaks free from Tapp but is killed by a tripwire trap, similar to the one in which her husband Steven was killed. Burdened by Melissa's death, Tapp becomes insane and is left in a functional asylum where he still believes he is playing Jigsaw's games.[5]

The game's sequel stated that Tapp escaped from Whitehurst and killed himself, thus confirming that the "Freedom" ending is canon.

Although Tapp is dead by the events of the game, the player assumed the role of his estranged son Michael, who tries to find the cause of his father's death, which leads him to conflict with Jigsaw. Michael came across case files by Detective Tapp, detailing events from the first film and his tests in Whitehurst Asylum from the first game. There are also audio tapes made by Tapp both before and after his Whitehurst Asylum tests that can be found throughout the game which detail his investigation of the Jigsaw Killer and his gradually building obsession, beginning with the discovery of Cecil's body. It is also revealed that Tapp felt guilty for killing Pighead in the first game, not knowing if the person in the costume had a family or if he was forced to work for Jigsaw.

Initially, Tapp is introduced in Saw as a typical police figure. When investigating the Jigsaw murders, Tapp begins to overlook police procedures and protocols in order to apprehend Jigsaw. This eventually gets his partner murdered and his own throat slashed. Tapp then becomes mentally unstable and develops an extreme obsession with Jigsaw to avenge his partner.[8] This evolution in Tapp's character eventually becomes his tragic flaw that leads to many misfortunes. The immediate consequences for this are his divorce from his wife and his discharge from the police force.[10]UGO described Tapp as "A good man who was driven mad by evil circumstances ..." and noted the choice he had between saving victims and catching Jigsaw.[11]

The obsession of Tapp to catch Jigsaw shown in Saw and the Saw: The Video Game has since been portrayed by several other characters in the Saw films. Key among these is Daniel Rigg, commander of the police department's SWAT team. Rigg, who had been subject to much trauma after witnessing several deaths at the hand of Jigsaw,[12] became obsessed with saving every victim who needed help. This caused Rigg to be placed in a series of tests in Saw IV so that he could let go of this obsession. Similar to the Freedom and Truth endings of Tapp's tests in Saw: The Video Game, Rigg could not let go of his need to save victims, which ultimately led to his own death, just like Tapp.[5][13][14]

Tapp bears similarities to other characters such as Peter Strahm and Eric Matthews. These characters share one tragic flaw; they prioritize catching Jigsaw over following police procedure. This is shown when both Tapp and Strahm refuse to call for back up upon following a lead on Jigsaw because of time restraints. In Saw, Tapp refuses to call for backup when he raided Jigsaw's lair. This causes Tapp to lose his partner Steven Sing and results in having his own neck slashed non-fatally. In Saw IV, Strahm calls for backup before entering Jigsaw's lair but does not wait for them to arrive. This nearly kills him after he is locked in a room alone and put into a test. In Saw V, Strahm follows Mark Hoffman to the nerve gas house from Saw II (now fully renovated) and pursues him into the basement. This time, he goes in without calling for backup, which results in him being killed by Hoffman's trap and left as a suspect due to being framed.[5][6][13][15]

This same flaw is also shown in a more obvious way in Saw II, where Eric Matthews chooses to ignore police interrogation procedure and instead degrades Jigsaw out of frustration because his son, Daniel Matthews was currently in Jigsaw's test at the time. Eric eventually beat Jigsaw, who was arrested earlier, against the rules of his test instead of waiting for the SWAT team to trace the location of his son's test. It would be later revealed that Daniel was safe because his test was recorded on video taken hours before. Rushing into the house without waiting to learn about the recordings, Eric makes his way into the underground bathroom used in Saw, where Amanda Young ambushes him, chains him to the pipes, and leaves him to die. Though he quickly escapes the room, he is soon re-captured and put into another game that ends in his death.

The flaws of the police figures in the films all come from prioritizing Jigsaw's arrest over following police procedure; this results in their eventual deaths.[5][16][17]

Tapp is shown to be an older male in his mid-50s during the first film's timeline. In contrast to many horror and action games, Tapp is not portrayed as superhuman or physically superior in any way. Being older, he is less fit and therefore inferior in combat situations. This is shown in Saw when Tapp loses a fistfight to Zep Hindle, which results in Tapp being shot in the chest. In the Saw: The Video Game, Tapp has a hard time wielding heavy weapons and is usually slower in attacking than his opponents.[5][18] Tapp's most distinguishing attribute, his thickly scarred neck, was acquired early in Saw; his scars have made his voice hoarse.[2][11] This feature allowed Adam Stanheight and Lawrence Gordon to identify Tapp easily when piecing together their abductions. Similar to other detectives in the Saw franchise, Tapp is seen wearing civilian clothing while on the police force; the exception is Saw V which shows a photograph of him in his uniform.[6]

Byron Hinson felt that Tapp's rendition in the Saw: The Video Game looked nothing like Danny Glover's Tapp from the film. He said that Tapp looked many years younger but partially blamed this on poor character textures and drawings.[19]MobyGames felt that while Earl Alexander did well at voicing Tapp for the game, he felt he sounded nothing like Danny Glover, which detracted from the game experience and pointed out the contradiction of Tapp's clear voice in the game despite his scarred throat. The reviewer went as far as to jokingly compare Earl Alexander's voice as being closer to Samuel L. Jackson's than Danny Glover's.[20]

During an interview with Spike, Danny Glover commented on his character, David Tapp, and his obsession, saying, "What happens in the process of trying to find him, I'm overcome because of this obsession I have. I mean most police detectives at least provide you with the image that they know everything, and they're so heady to some extents, so above the others that we can figure this stuff out. But the process of figuring this stuff out, as I come closer to this, I come closer to something else that's happening and maybe I come closer to my own fear to some extent. And certainly my worst fears come to bear when I'm shot, and wounded, and my partner is killed. Then there's another level of obsession that now translates itself into this film or becomes apparent in this film. And the obsession that's connected with anger and guilt, to some extent, along with fear is pretty potent in this sense. and all of that brings about a kind of psychological breakdown, a psychotic breakdown in terms of this character. I think the obsession in some sense drives us, you know? It's obsession that drives you in a different way that's not fulfilled or completed in some way. It certainly leaves a whole 'nother kind of space there that is a very dangerous space for Tapp, the police man. Certainly coupled with the fact that my partner is lost because of essentially my own inadequacy because of me. That transforms the situation."[21]

In the same interview, Glover commented on his attraction to the film and the prospect of playing Tapp in Saw, stating, "I saw 10-12 minutes of video of the first scene here and I was really impressed with it. I was impressed by the way of the shot, the way the camera moved, and the kind of subtlety and the language of the story. Sometimes you look at a story and you're looking at the language of the story and how does the person use language, you know? and I like all of that how does the director or the filmmaker use language in order to shape or tell the story, and I like that."[21]

^Saw II special edition (DVD)|format= requires |url= (help). Lions Gate Entertainment. 2006. Jigsaw: It was the police and the press who coined the nickname Jigsaw. I never encouraged or claimed that. The jigsaw piece that I cut from my subjects was only ever meant to be a symbol that that subject was missing something. A vital piece of the human puzzle. The survival instinct.

^Saw V (DVD)|format= requires |url= (help). Lions Gate Entertainment. 2009. Hoffman: There is another detective that you should be aware of. His name's Tapp. He's smart, and he's getting closer. John: I know who he is. I need you to lead him to someone for me. A doctor. A healer who needs some healing.